The attitude of an artificial satellite is controlled on the basis of information provided by an onboard gyro package or positional information of the earth or the sun.
An arrangement for controlling such an attitude in the prior art has been discussed by R. L. Farrenkopf, entitled "Generalized Results for Precision Attitude Reference Systems Using Gyros", AIAA paper, No. 74-903, 1974, wherein a filter algorithm which provides high precision attitude determination on an assumption that the observed values and catalog values of a fixed star is given by some means and the initial attitude of the satellite is predetermined.
Further, techniques are described by R. J. Jude, entitled "System Study of an Internal Attitude-Measurement System for Earth Pointing Satellites", Proceedings of AOCS Conference, Filed in Noordwijk, 3-6, October, 1977 (ESA SP-128. November 1977), wherein a decision is made on the deviation between body axis of the satellite to be directed to the earth and the direction of the center of the earth on the basis of the estimated values of star vector based on objective attitude calculated by the use of orbit data.
Furthermore, an arrangement for maintaining the high precision of the attitude determination system and, in particular, method for formating filters are described by K. Yong, et al., entitled "Realtime Precision Attitude Determination System (RETPAD) for Highly Maneuverable Spacecrafts" AIAA G&C Conf., p48, (7-9 August, 1978).
A conventional attitude control system of such an art which has been developed previously is shown in FIG. 1A, in which respective directions of the fields of view of a first and second earth sensor are rotated about axes X.sub.B and -X.sub.B respectively to detect the pitch deviation .theta. and the roll deviation .phi. between the body axes (Y.sub.B, Z.sub.B) and (X.sub.B, Z.sub.B) and a direction of the center of the earth E. More particularly, the roll deviation .phi. is detected, as shown in FIG. 1C, on the basis of the difference between the earth scanning widths of the first and second earth sensors, while the pitch deviation .theta. is detected on the basis of the deviation of the reference pulse from the center of the scanning pulse, as shown in FIG. 1D. As shown in FIG. 1B, the attitude of the satellite is controlled so that those deviations are reduced to zero.
However, it is known that the detecting output from the earth sensor is subject to the influence of the variation of the atmosphere in radiation, and hence it has been difficult to control the attitude of the satellite in high precision. Furthermore, since only the deviation of the attitude is the subject of attitude compensation control in such an attitude control system, it has been difficult to control the attitude changing speed so that the speed will coincide with a reference value simultaneously with the control of the attitude itself.